Fiber reinforced ceramic matrix laminate
AssigneeThe Boeing Company
InventorsKristina S. Preedy, Frederick H. Simpson
Life of this patent
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Abstract
Tough ceramic products can be prepared without exotic pressure fabricating techniques by use of a matrix laminate comprising a continuous fiber ceramic reinforcement in tow or woven form for strength, stiffness, and toughness and a ceramic matrix generally comprising (a) a filler, such as mullite; (b) ceramic reinforcing whiskers, such as silicon nitride or silicon carbide, for fine-scale interlaminar shear resistance (c) a binder, such as colloidal silica; and (d) an activator, such as a trona-like material including sodium and carbonate. The matrix is brushed into the fiber reinforcement, which is then laid up, dried, and cured. Tandem ceramic composites can be fabricated.
Claims18
A reinforced ceramic matrix laminate suitable for lay-up and cure at low temperatures and at ambient pressure to yield tough, cured ceramics and having both coarse and fine-scale reinforcement, comprising:
- (a) a continuous ceramic fiber reinforcement in tow or cloth form to provide coarse reinforcement for improving strength, stiffness, and toughness;
- and
- (b) a cementitious matrix including a cementitious filler, reinforcing whiskers of silicon nitride or silicon carbide to provide fine reinforcement for improved interlaminar shear resistance, and a binder that contains colloidal silica.
A fiber reinforced ceramic having a high toughness as exhibited by its non-linear stress-strain characteristics when tested in flexure, and a flexural stress of between about 10,000-20,000 psi in 3-point bending achieved without hot pressing, comprising:
- (a) a continuous ceramic fiber reinforcement in tow or cloth form for strengthening, stiffening, and toughening;
- and
- (b) a matrix including a mullite filler;
- reinforcing whiskers selected from the group consisting of SiC, Si.sub.3 N.sub.4, or mixtures thereof for fine-scale interlaminar shear resistance;
- a colloidal silica binder;
- and an activator that is a trona-like material including sodium and carbonate,
- wherein the ceramic is prepared by:
- (i) mixing the whiskers and binder;
- (ii) adding the filler and activator to form the matrix;
- (iii) mixing the matrix;
- (iv) applying the matrix to the reinforcement;
- (v) working the matrix into the reinforcement to form a ceramic laminate;
- (vi) drying the laminate in air at ambient pressure;
- (vii) heating the laminate at ambient pressure and to further dehydrate the matrix;
- and
- (viii) increasing the flexural strength of the laminate by heat treating the dried laminate at ambient pressure and at a temperature in excess of 1000.degree. F.
A method for making a fiber reinforced ceramic, comprising the steps of:
- (a) sonicating a mixture of ceramic whiskers and a binder to form a substantially well mixed mixture substantially free from agglomerated whiskers;
- (b) adding a ceramic filler and an activator to the mixture of step (a) for form a matrix paint;
- (c) sonicating the matrix paint to mix the matrix paint;
- and
- (d) applying the matrix paint to a fiber reinforcement.
A method for making a ceramic composite using a fiber reinforced ceramic matrix laminate comprising the steps of:
- (a) preparing a ceramic laminate by infusing a ceramic matrix, comprising a ceramic filler, ceramic reinforcing whiskers for improved interlaminar shear resistance at a fine scale, a binder, and an activator, into a continuous fiber reinforcement in tow or cloth form;
- (b) laying up the laminate on a mold;
- (c) drying the laminate in air at ambient pressure;
- and
- (d) increasing the flexural strength of the dried laminate by heat treating the laminate at ambient pressure in air at an elevated temperature.
Dependencies are inferred from the claim text.